Identification of suberization-associated anionic peroxidase as a possible allergenic protein from tomato.

A 45 kDa protein, which is recognized by IgE antibodies in sera of food-allergic patients, was purified and characterized as an allergenic protein from the tomato. The IgE-binding protein purified from tomato extract was found to be a glycoprotein with a molecular weight of approximately 45,000, an isoelectric point of 4.2, and no free N-terminal amino group. Furthermore, it was shown that the purified protein had peroxidase activity. From the amino acid sequence of a peptide fragment prepared by lysylendopeptidase digestion, the allergenic protein was identified to be the tomato suberization-associated anionic peroxidase 1 known as one of the pathogenesis-related proteins widely distributed in plants. These properties suggested the protein isolated from tomato to be a new allergenic protein in plant foodstuffs.